Radiation tracking for portable fluoroscopy x-ray imaging system

ABSTRACT

A method for fluoroscopy energizes a radiation source to form a scout image on a detector and processes the scout image to determine and report a radiation field position with respect to a predetermined zone of the detector. The radiation source is energized for fluoroscopic imaging of a subject when the reported radiation field position is fully within the predetermined zone.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/937,624, filed on Jul. 24, 2020, entitled “RADIATION TRACKING FORPORTABLE FLUOROSCOPY X-RAY IMAGING SYSTEM”, in the name of Richard etal., which is a continuation of U.S. patent application Ser. No.16/221,662, filed on Dec. 17, 2018, entitled “RADIATION TRACKING FORPORTABLE FLUOROSCOPY X-RAY IMAGING SYSTEM”, in the name of Richard etal., which claims the benefit of U.S. Provisional application U.S. Ser.No. 62/685,473, provisionally filed on Jun. 15, 2018, entitled“RADIATION TRACKING FOR PORTABLE FLUOROSCOPY X-RAY IMAGING SYSTEM”, inthe name of Richard et al., hereby incorporated by reference herein inits entirety.

TECHNICAL FIELD

The disclosure relates generally to the field of digital medical imagingand in particular to digital medical imaging for fluoroscopy. Morespecifically, the disclosure relates to a radiation source trackingmethod for a portable fluoroscopy x-ray imaging system.

BACKGROUND

Fluoroscopic imaging is valued as a useful tool for practitionerguidance during surgery or other interventional or diagnostic procedure.Using fluoroscopic apparatus, the practitioner can obtain real-timevideo feedback on aspects of a surgical procedure, on positioning oftubing or other hardware, flow of a contrast agent, or activity of aparticular organ. In conventional fluoroscopic imaging systems, theradiation source and detector are mechanically coupled, so that theirposition, relative to each other, has a rigid, fixed geometry. Alignmentof the x-ray source to detector is not adjustable to the operator, butis fixed by the imaging system mechanics.

The advent of portable digital radiography (DR) detectors advancesradiographic imaging and makes it possible to improve patient access toimaging services, such as in situations where it can be risky or awkwardto move the patient for a procedure. An area where this can be ofparticular utility is in the intensive care unit (ICU), where multiplesupport systems may need to be used for a particular patient.

One difficulty with the use of portable DR detectors relates to data onrelative source-to-detector positioning, which is no longer inherentlyprovided by the imaging system. Aspects of positioning that are ofparticular importance for fluoroscopy include positioning the source sothat it is perpendicular with the detector and field limitation,controlling the radiation field size and direction so that the primaryradiation field lies fully on the detector.

Various source-detector alignment approaches have been proposed forsystems having the DR detector mechanically decoupled from the source.These approaches have included the use of various instruments to detectskew, orientation, source-image distance, and other aspects ofpositioning for these components. Other approaches have included the useof an initial exposure that directs a pattern of alignment beams towardthe detector for sensing and calculation of skew error. While there issome merit in such approaches, however, they are largely directed toportable radiography itself, rather than to specific requirements offluoroscopy, Characterized by lower levels of radiation and real-timedisplay of image content at lower resolution, fluoroscopy is a guidancetool that helps the practitioner to visualize the progress of aprocedure rather than to diagnose the condition of internal hone ortissue.

There are a number of considerations and requirements of conventionalradiographic practice that are poorly suited for the fluoroscopyenvironment. This can be appreciated, for example, in consideringdifferences between serial radiography, in which a series of exposuresis acquired in a timed sequence using standard radiographic strictures,and fluoroscopy, in which a series of exposures is rapidly acquiredunder very different working conditions and generally at lower dosageand, consequently, lower resolution. In serial radiography, theradiographer and any attending staff move away from the imaged subjectuntil the series of exposures completes and the images are generated anddisplayed. In fluoroscopy, on the other hand, the sequence of exposuresis acquired and displayed with the practitioner and staff positionedclosely about the patient and, consequently, very near to the radiationfield.

Distinctions between radiography and fluoroscopy environments andpractices have been recognized by regulatory agencies, along with anawareness of the advantages and risks of portable detector use. As oneresult, there are different requirements for beam accuracy in light ofthese differences.

FIG. 1 summarizes some of the separate regulatory requirements that havebeen adopted for radiographic and fluoroscopic devices. Under theradiography regulations certain exemptions are given for devices usingportable detectors. The exemptions relate to risk/benefits concerns forthe patient, obtained when source and detector are uncoupled, whichenables imaging at a beside but limits the ability to meet certainregulations. Specifically, exemptions deal with field limitation andradiation path perpendicularity. As such, there are challenges, whenusing fluoroscopy with a portable detector, in meeting equivalentrequirements related to conventional fluoroscopic regulations.

It may not always be possible to fix the relative positions of sourceand detector relative to the patient for the full fluoroscopy sequence.For example, in ICU and other environments in which fluoroscopy is used,there can be unwanted movement by the patient and the need forreadjustment of source position during the imaging session.Repositioning may alternately be needed in fluoroscopy for variousreasons, such as when the source or its supporting structure isaccidentally jostled and shifted in position during a procedure.

Thus, it can be recognized that there is a need for solutions that meetregulatory guidelines for beam coverage and perpendicularity withportable DR detectors used in fluoroscopy applications. Of particularconcern is the need to provide fluoroscopy using portable DR detectorswhile limiting exposure to the treatment region and away from theattending medical team and from other regions of patient anatomy.

SUMMARY

An object of the present disclosure is to address the need for improvedradiation tracking for fluoroscopy x-ray imaging systems using portableDR detectors.

These objects are given only by way of illustrative example, and suchobjects may be exemplary of one or more embodiments of the disclosure.Other desirable objectives and advantages inherently achieved by the mayoccur or become apparent to those skilled in the art. The disclosure isdefined by the appended claims.

According to an aspect of the present disclosure, there is provided amethod for fluoroscopy comprising: energizing a radiation source to forma scout image on a detector; processing the scout image to determine andreport a radiation field position with respect to a predetermined zoneof the detector; and energizing the radiation source for fluoroscopicimaging of a subject when the reported radiation field position is fullywithin the predetermined zone.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of exemplary embodiments of the invention, as illustrated inthe accompanying drawings. The elements of the drawings are notnecessarily to scale relative to each other.

FIG. 1 is a chart that gives a summary view of the regulatory landscapefor radiography and fluoroscopy systems using fixed and portabledetectors.

FIG. 2 is a schematic diagram that shows an x-ray imaging field incidenton the active imaging area of a digital radiography detector.

FIG. 3 is a schematic diagram that shows an x-ray imaging field incidenton the active imaging area and within a safe zone of a digitalradiography detector.

FIG. 4 is a schematic diagram that shows an x-ray imaging field incidenton the active imaging area and within a warning zone of a digitalradiography detector.

FIG. 5 is a schematic diagram that shows an x-ray imaging field incidenton the active imaging area and extending into a termination zone of adigital radiography detector.

FIG. 6 is a perspective view of a mobile digital radiographic (DR)imaging system.

FIG. 7 is a perspective view showing source and detector positioning fora mobile digital radiographic (DR) imaging system.

FIG. 8 is a perspective view of patient imaging using a mobile digitalradiographic (DR) imaging system.

FIG. 9 is a perspective view of a mobile digital radiographic (DR)imaging system.

FIG. 10A is a perspective view showing an outline of a radiation fieldin a Safe zone defined on the detector.

FIG. 10B is a perspective view showing an outline of a radiation fieldin a Warning zone defined on the detector.

FIG. 10C is a perspective view showing an outline of a radiation fieldin a Termination zone defined on the detector.

FIG. 11 is a logic flow diagram showing a sequence for fluoroscopyimaging according to an embodiment of the present disclosure.

FIG. 12 is a plan view showing an operator interface for zone andparameter setup.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following is a detailed description of the preferred embodiments,reference being made to the drawings in which the same referencenumerals identify the same elements of structure in each of the severalfigures.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more”. In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B”. “B but not A”, and “A and B”, unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein”. Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, or process that includes elements in addition to those listedafter such a term in a claim are still deemed to fall within the scopeof that claim.

In the following claims, the terms “first”, “second”, and “third”, andthe like, are used merely as labels, and are not intended to imposenumerical or ordinal requirements on their objects.

In the context of the present disclosure, the terms “viewer”,“operator”, “viewing practitioner” “observer”, and “user” are consideredto be equivalent and refer to the viewing practitioner or other personwho views and manipulates an x-ray image on a display monitor or otherviewing apparatus.

As used herein, the term “energizable” relates to a device or set ofcomponents configured to perform an indicated function upon receivingpower and, optionally, upon receiving an enabling signal.

The term “actuable” has its conventional meaning, relating to a deviceor component that is capable of effecting an action in response to astimulus, such as in response to an electrical signal, for example.

The term “modality” is a term of art that refers to modes or types ofimaging. Modalities for an imaging system may be conventional x-rayradiography, fluoroscopy or pulsed radiography, tomosynthesis,tomography, ultrasound, MMR, or other types of imaging. The term“subject” refers to the patient who is being imaged and, in opticalterms, can be considered equivalent to the “object” of the correspondingimaging system.

The terms “image” and “image data” can be used interchangeably in thecontext of the present disclosure. An image that is captured by animaging apparatus is processed, displayed, transmitted, and stored asimage data.

Applicants' disclosure is directed to satisfying performance objectivesof fluoroscopy regulations while maintaining advantages of the decoupleddetector. Applicants' disclosure focuses on field limitation, whichensures that the primary radiation is directed fully within the detectorboundary during fluoroscopic captures.

Proper field limitation ensures that all of the primary radiation of theradiation field is contained within the image receptor. This isimportant so as to minimize dose to the patient and reduce exposure riskto the staff.

Fluoroscopy differs from conventional radiography in a number of ways.In fluoroscopic imaging, for example, an operator control, typically afoot pedal as described subsequently, is used as a type of switch forenergizing the radiation source to generate exposures. According to anembodiment of the present disclosure, this operator control is enabledwhen the detected radiation field is in appropriate position relative tothe detector. This can mean that the energization current is availablefor energizing x-ray emission when these field conditions aredetermined. Operation of the foot pedal or other control then causes thecircuit connection to complete, so that the radiation source isenergized and emits radiation. If the control is disabled, the operatorcannot cause x-ray emission to occur without using an override controlor command.

With conventional workflow, fluoroscopy systems typically do not includea collimator light field. Conventional fluoroscopy systems directradiation through the patient to an electronic detector that providesvideo output on a display monitor. The extent of the x-ray source fieldor field boundaries are often not visible to the operator. Therefore,for such systems, initial setup is performed by visually aligning thefluoroscopy assembly to the patient. At this point, acquisition of asingle fluoroscopy image frame, or of a few exposures, confirms initialpositioning. Adjustments are made and the exposure level is set via anautomatic brightness control. Field limitation is automatically achievedvia the structural linkage, with fixed positioning maintained betweenradiation source and detector.

Applicants' disclosure provides/describes an alternate workflow toprovide suitable field limitation with a portable DR detector.

Applicants note that fluoroscopy requires that the x-ray source/tube anddetector be aligned such that all of the x-ray radiation field iscaptured by the digital detector. This alignment is inherent inconventional fluoroscopy systems when source and detector aremechanically coupled. However, systems using portable DR detectors thatare not mechanically coupled to the source are not able to readilydetermine or provide source/detector alignment and consequent control ofradiation field position prior to imaging. This disclosure provides amethod to track, warn, and/or terminate the x-ray radiation if theradiation field impinges upon or exceeds predetermined/preset boundariesof the portable DR detector. More particularly, x-ray emission from thetube/source is terminated automatically if the radiation field impingesand/or falls outside of the digital detector. Applicants' method thusdoes not require the use of a mechanical linkage between the tube/sourceand digital detector for sensing incorrect positioning of the radiationfield.

According to an embodiment of the present disclosure, visibleillumination, coupled to the x-ray source and emitted through thecollimator, can be used to help guide source positioning. While in thefluoroscopy mode, the collimator illumination is automatically turned onto provide assistance for positioning the tube over the patient and thedetector.

The collimator illumination remains on throughout the fluoroscopy exam.In addition, the appearance of the collimator illumination can bechanged to indicate the status of radiation field positioning. Thus, forexample, the collimator illumination can be white light when theradiation field is detected in a suitable position for fluoroscopy, suchas within the Safe zone, as described subsequently. Detection of theradiation field within other zones of the detector, such as the Warningand Termination zones described subsequently, can cause a change in theillumination color. Appearance change can also relate to blinking,intensity variation, patterning, or other feature of the illumination orportions of the illumination field.

A scout image, which is a low-dose radiograph optimized for the regionbeing imaged, is acquired both (i) to confirm position and,additionally, (ii) to assess the field limits. The scout image isacquired with one set of technique settings, such as can be used forradiographic imaging, for example. Subsequent fluoroscopy imaging canthen use a different set of technique settings. The scout andfluoroscopy images can have the same field dimensions.

Software automatically analyzes the scout image to ensure that theentire radiation field is within the boundary of the detector. Thesystem does not enable fluoroscopic acquisition until this condition ismet.

Because the majority of system technicians/operators are currentlytrained to use a light field for portable radiography alignment andbecause the detector is larger than the typical ROI (Region of Interest)for a fluoroscopic procedure, the likelihood of the radiation fieldbeing outside the detector during scout image acquisition is expected tobe low.

According to an embodiment of the present disclosure, the relativeposition of the radiation field is tracked by defining and monitoring aseries of zones within the digital radiography detector. Zones aredefined and prioritized based on relative proximity to outer edges ofthe detector. Detection of radiation in the outermost zones, nearest theedges, indicates the need to adjust the position of the x-ray source orto de-energize the x-ray source altogether, terminating fluoroscopyimaging until positioning of the radiation field is corrected. Thus, asto radiation tracking during fluoroscopy, tracking of the radiationduring fluoroscopic acquisition is used to provide warning andtermination (an optional feature/step/process) of the x-ray undercertain conditions. The sequence of FIGS. 2, 3, 4, and 5 describesexamples of different possible conditions for x-ray field positioning.

For example, referring to FIG. 2 , there is illustrated an x-ray imagingfield 20 incident on the active imaging area of a digital radiographydetector 10. Although radiation field 20 may be skewed with respect tothe edge borders or outline of the active DR detector 10 imaging field,the full field 20 lies well within the active DR detector 10 imagingfield.

Referring to the example of FIG. 3 , the preferred position of x-rayfield 20 is within a safe zone S of detector 10, shown in dashedoutline. The technician or other operator of a fluoroscopy systemtypically aims x-ray field 20 so that the primary radiation is incidenton detector 10, with none of x-ray field precariously close to, or lyingbeyond, any edge of detector 10. The safe zone S region that is definedfor fluoroscopy is disposed well within the available imaging field ofthe detector as shown.

Referring to the schematic diagram of FIG. 4 , a second region isdefined, Warning zone W, extending from the periphery of the safe zone Sand still within the active imaging area of the detector 10. In apreferred arrangement, the Warning zone W is a few centimeters wide,which can be suitable for conventional fluoroscopy applications;dimensions for defining zone W boundaries can vary widely, as can bereadily appreciated by those skilled in the radiographic arts.Preferably, the Warning zone W surrounds sides/edges/boundaries of theSafe zone S. In an alternate embodiment, it may be sufficient to definethe Warning zone W along at least one side/edge/boundary of the Safezone S.

In a preferred arrangement, if any portion of the primary/designatedx-ray radiation field 20 is incident within Warning zone W, a warningsignal is generated and a warning message or other warning indicationresults and is reported, displayed to the operator. Such a warningindication could be audible or visible, for example. A visible warningcould include a message, text, symbol, icon, marker or the likedisplayed on a monitor/display or projected to appear on the patient.Similarly, the warning could be a message, text, symbol, icon, marker orthe like sent to the user's mobile device/tablet.

According to an alternate embodiment of the present disclosure, awarning indication can also be provided by a collimator light thatprovides illumination that is visible to one or more members of thefluoroscopy team. The color of the collimator light can be changed toindicate a warning condition; alternately, flashing or other lightbehavior can be used for warning indication.

Referring to FIG. 5 , a third/another region, extending from the outerboundary of the Warning zone W to the inner edges of the detector 10imaging area, serves as a termination zone Z. If any portion of theradiation field primary/designated beam extends into Termination zone Z,there is the potential for some portion of the exposure energy to bemisdirected past an edge of DR detector 10. To prevent this condition,control logic for the fluoroscopy apparatus can continually sense forany portion of the emitted radiation field in zone Z and generate anappropriate signal for reporting positioning status.

In the event of detection of x-ray radiation within Termination zone Z,x-ray energy is turned off. Following this action, after correcting theaim or alignment of the source, the user/operator could immediatelyresume the study by initiating a scout image. The Termination zone Z isdisposed within the detector field.

Optionally, a warning can be displayed to the operator when theradiation field extends outside of the Safe zone S to either or bothWarning zone W and Termination zone Z. Such a warning could be audibleor visible. A visible warning could include as a message, text, symbol,icon, marker or the like displayed on a monitor/display. Similarly, itcould be a message, text, symbol, icon, marker or the like sent to theuser's mobile device/tablet. The warning may, include instructions tothe user/operator to immediately resume the study with a scout image.Alternately, an indication could be projected onto the surface of thepatient, using the collimator light or a related projector.

In a preferred arrangement, the Termination zone Z can be a fewcentimeters wide. Preferably, the Termination zone Z surrounds allsides/edges/boundaries of the Warning zone W. In an alternateembodiment, it may be sufficient to define the termination zone Z alongat least one side or edge of the warning zone W.

In addition, the collimator light that shows the radiation fieldboundaries can remain on continuously, or can be flashing, during andbetween acquisitions in fluoroscopic mode, providing instant visualfeedback on positioning to the practitioner and staff. Additionalfeedback can be provided by changing color of the collimatorillumination, such as to indicate whether or not the radiation field isdetected solely within the Safe zone S or impinges upon Warning zone Wor Termination zone Z.

This disclosure describes a system and method of radiation tracking fora portable fluoroscopy x-ray imaging system, wherein the systemcomprises an x-ray source, a collimator, and a freely positionable DRdetector that is uncoupled from the x-ray source. The method includes:positioning the x-ray source and the DR detector about a patient;adjusting an aperture of the collimator to a predetermined size known togenerate an x-ray radiation field to substantially fit within theborders of the DR detector; determining a Safe zone region surroundingthe x-ray radiation field and within the borders of the detector;determining a Warning zone region surrounding the Safe zone and fullywithin the borders of the detector; determining a Termination zoneregion surrounding the Warning zone; and operating the imaging system ina fluoroscopy mode by: (i) activating the x-ray source; (ii) using theactivated x-ray source, iteratively, acquiring a digital image on the DRdetector; (iii) determining if the x-ray radiation field of the x-raysource used to acquire the digital image impinges the Safe zone, Warningzone, or Termination zone; (iv) providing a warning if the x-rayradiation field impinges the Safe zone or Warning zone, and (v)deactivating the x-ray source if the x-ray radiation impinges theTermination zone.

Reference is made to PCT/US18/24274, filed on Mar. 26, 2018, entitledBEDSIDE DYNAMIC IMAGING, in the names of O'Dea et at, incorporatedherein in its entirety by reference.

When an x-ray image is obtained, there is generally an optimal distanceand angle between the radiation source and the two-dimensional digitalradiography (DR) detector that records the image data. In most cases, itis preferred that the x-ray source provide radiation in a direction thatis generally perpendicular to the surface of the DR detector. For thisreason, large-scale radiography systems mount the radiation head and theDR detector holder at a specific angle relative to each other. Orientingthe radiation head and the DR detector typically requires a C-arm ofsubstantial size, extending outward well beyond the full distancebetween these two components. With such large-scale systems,source-to-image distance (SID) is tightly controlled and unwanted tiltor skew of the DR detector is thus prevented by the hardware of theimaging system itself. Further, because the spatial positioning andgeometry of conventional large-scale systems is well-controlled, properalignment of the x-ray source and DR detector is inherent andstraightforward.

Mobile x-ray apparatus are of particular value in intensive care unit(ICU) and other environments where timely acquisition of a radiographicimage is important. Because it can be manually wheeled around the ECU orother area and brought directly to the patient's bedside, a mobile x-raysystem allows an attending physician or clinician to have up-to-dateinformation on the condition of a patient and helps to reduce the risksentailed in moving patients to stationary equipment in the radiologicalfacility. With the advent of mobile radiation imaging systems, such asthose used in intensive Care Unit (ICU) environments, a fixed angularrelationship between the radiation source and two-dimensional DRdetector, and accompanying grid, if any, is no longer maintained by themounting hardware of the system itself. Instead, an operator is requiredto aim the radiation source toward the DR detector imaging surface,providing as perpendicular an orientation as possible, typically using avisual assessment. The DR detector itself, however, may not be visibleto the technician once it is positioned underneath or behind thepatient. This complicates the alignment task for mobile systems,requiring some method and apparatus for measuring SID (source-to-imagedistance) and tilt angle, and making it more difficult to use a grideffectively for reducing the effects of radiation scatter.

Current portable radiation imaging systems allow some flexibility forplacement of the DR detector by the radiology technician. The patientneed not be in a horizontal position for imaging, but may be at anyangle, depending on the type of image that is needed and on the abilityto move the patient for the x-ray examination. The technician canmanually adjust the position of both the DR detector and the radiationsource independently for each imaging session. Thus, it can beappreciated that a system for determining SID and angle between theradiation source and the DR detector must be able to adapt to whateverorientation is best suited for obtaining a particular radiographicimage.

Referring to FIGS. 6-9 , there is shown a perspective view of a mobiledigital radiographic (DR) imaging system 400 that may include: aprocessing console 420, embodied as a wheeled mobile x-ray cart 900having a processing system 421 that provides control logic circuitry,such as a computer or dedicated control logic unit (CPU) with electronicmemory therein, a generally planar DR detector 404, an x-ray source 408configured to generate radiographic energy, a collimator 401 to shapethe x-ray beam 403 emitted by source 408, and a digital monitor 422configured to display radiographic and fluoroscopic images captured bythe DR detector 404, according to one embodiment. The processing console420 may also include a digital monitor thereon similar in operation tothe digital monitor 422. The DR detector 404 may include atwo-dimensional array of addressable photosensitive cells (pixels) asdescribed herein above. The DR detector 404 may be positioned to receivea collimated x-ray beam 403 passing through a patient 406 lying on a bed407 during a radiographic fluoroscopy session. The mobile radiographicimaging system 400 may use an x-ray source 408 that emits collimatedx-rays, e.g. an x-ray beam 403, selectively aimed at and passing througha preselected region of the subject patient 406. The DR detector 404 ispositioned underneath patient 406 in a perpendicular relation, as muchas possible, orthogonal to a substantially central ray 17 of the x-raybeam 403. The location of particular pixels in detector 404 may berecorded according to column and row as described herein, in order todetermine a distance between selected ones of the pixels. The density ofpixels in a particular DR detector is known. For example, the pixeldensity may include any one designed pixel density selected from a rangeof between about ten pixels per millimeter to about twenty pixels permillimeter in one or both rectilinear (column×row) dimensions of theplanar DR detector 404.

The photosensitive cells of detector 404 are read out by digital imageprocessing electronics described herein to be eventually displayed onthe digital monitor 422 for viewing (luring a fluoroscopic imagingsession.

The read-out electronics may communicate with a processing console 420over a wireless transmitter to transmit fluoroscopic image data thereto.

The processing console 420 includes a processing system havingelectronic memory and may also be used to control the x-ray source 408,the aperture size and shape of the electronic collimator 401, and aprojection angle of the x-ray beam 403 relative to the tube head 405 bymanipulating the electronic collimator aperture, the tube head 405electric current magnitude, and thus the fluence of x-rays in x-ray beam403, and thus the energy level of the x-ray beam 403. The processingconsole 420 may transmit images and other data to the connected digitalmonitor 422 for display thereon.

The processing system of processing console 420 may also be used toselectively identify pixels in the array by a row×column index forhaving absorbed a particular amount of radiographic energy, such as ahigh intensity and energy level, and to record the row and columnindices of those pixels for source-to-image distance and tiltcalculations, as described herein.

A portion or all of the processing console 420 functions may reside inthe detector 404 in the on-board processing system as described herein.

DR detector 404 may include a three-dimensional, or three-axis,inclinometer, which may be referred to herein as an accelerometer,inertial sensor, or tilt sensor. In one embodiment, the DR detector 404may be configured to transmit its three-dimensional tilt coordinates tothe processing console 420. In one embodiment, the DR detector 404, withan inclinometer 503 may be configured to receive three-dimensional tiltcoordinates transmitted from the collimator 401, which may include itsown separate three-dimensional inclinometer. In one embodiment, both theDR detector 404 and the collimator 401 may be configured to transmittheir three-dimensional tilt coordinates to the processing console 420.

The recipient of the three-dimensional tilt coordinates, the processingconsole 420 or the DR detector 404, may be configured to calculate arespective planar position of the DR detector 404 and the collimator 401to determine an angular displacement of the DR detector 404 and/or thecollimator 401 relative to a parallel orientation thereof. The angulardisplacement so determined may be displayed on the monitor 422, whichdisplacement may include a calculated displacement having a zero valuewhich indicates that the collimator 401 and the detector 404 aredisposed parallel to each other. The angular displacement may include acalculated displacement having a 30° value which indicates that thecollimator 401 and the detector 404 are displaced from a parallelorientation by 30°.

The x-ray source 408 and collimator 401 taken together may be referredto herein as a tube head 405, The collimator 401 may include anelectronic collimator 401 that is configured to communicate wirelesslywith the detector 404 or with the processing console 420. The collimator401 may communicate three-dimensional coordinates 505 as determined byits connected inclinometer. The collimator 401 may communicate data onpositions of the collimator blades that shape its aperture, such aswidth and length dimensions of the collimator aperture, for example. Asdescribed herein, the collimator 401 may include a three-dimensionalinclinometer configured to dynamically transmit measuredthree-dimensional tilt coordinates to the detector 404 and/or to theprocessing console 420. Collimator blades contained in the electroniccollimator 401 control a shape and size of an aperture of the collimatorand, thereby, an exposure area on the detector 404, which exposure areareceives x-rays of the x-ray beam 403 generated and emitted by the x-raysource 408. The pixels in the exposure area, or radiation field,transition to a charged state upon receiving x-ray radiation. Thecollimator blades may be configured as a pair of parallel blades forminga rectangular aperture, which blades may be individually adjustableunder programmed motor control.

Control instructions for adjusting the electronic collimator aperture501 may be transmitted from the processing console 420, which may alsoreceive positioning feedback data from the collimator 401 indicatingprecise height and width dimensions of the electronic collimatoraperture 501, which precise height and width dimensions may then benumerically displayed on the digital display monitor 422.

A collimator light 502 can provide illumination that serves as a guideto the location of the radiation field, as well as indicating relativeposition of the radiation field.

The wheeled mobile cart containing processing console 420 may be usedtogether with the display monitor 422 supported by a lightweight stand424. Wheels 427 may be attached to the lightweight stand 424 via aplurality of stabilizing legs 425 for rolling the stand 424 across asurface, such as a floor, together with the processing console 420. Afoot pedal assembly 426 having one or more pedals may be configured toinitiate and terminate serial radiographic image acquisition(fluoroscopy). The foot pedal assembly 426 may also be configured toswitch the mobile radiographic imaging system 400 into alternateoperating modes, such as between a fluoroscopic imaging mode and astandard single image projection radiography mode.

FIG. 9 is a perspective view of the wheeled mobile x-ray cart 900 of themobile digital radiographic imaging system 400. FIG. 9 depicts the majorcomponents of the mobile radiographic imaging system 400 in their stowedpositions on the wheeled mobile x-ray cart 900 which are configured forrollably transporting the mobile radiographic imaging system 400 in apatient care facility. An advantage of the mobile radiographic imagingsystem 400 is that serial radiography (e.g., fluoroscopy) becomescompletely mobile in nature because the necessary components are easilytransportable to a patient bedside using the wheeled mobile x-ray cart900. When it is desired for the mobile radiographic imaging system 400to be used for general purpose radiography, the hardware describedherein for serial radiography may be used for general purpose imaging.

As shown in FIG. 9 , a storage nest 901 is configured to store thelightweight stand 424. A feature of the stand 424 is that thestabilization legs 425 can be folded to minimize required space fortransport, and storage nest 901 is configured to receive the legs 425 ina folded state. An upper restraint 902 has a nesting feature assemblysized to receive the pole of the stand 424 and includes a flexible strapto secure it. Monitor storage 903 is used to secure the digital display422 during transport. The digital display 422 may be inserted into themonitor storage 903 in the direction indicated by the correspondingarrow. Monitor storage 903 is formed as a continuous and rounded shapesuch that it does not snag or inhibit movement of high voltage cablesthat may drape along the mobile radiographic imaging system 400. Footpedal assembly storage 904 is used to secure the foot pedal assembly 426during transport. The foot pedal assembly 426 may be inserted into thefoot pedal assembly storage 904 in the direction indicated by thecorresponding arrow. A feature of the foot pedal assembly 426 is anexternal groove configured to receive its connectivity cable beforeinsertion into the foot pedal assembly storage 904. The bottom of thevertical support column 905 is attached to, and is rotatable relativeto, the wheeled transport frame 907 which contains the processingconsole 420. The tube head comprising x-ray source 408 and electroniccollimator 401 is attached to one end of a horizontal boom 906 which, inturn, is attached to a top end of the vertical support column 905. Thetube head is configured to be movable to a variety of angular positionswith respect to horizontal boom 906.

Still referring to FIGS. 6-9 , there is described a method of operatinga mobile fluoroscopic imaging system wherein an x-ray source and adigital radiography (DR) detector are manually positioned about apatient. Data defining a spatial configuration of the x-ray source andthe collimator is stored in the system. The system is configured todetermine a source-to-image distance of the x-ray source and the DRdetector by activating the x-ray source and capturing a scout image inthe DR detector. Dimensions of the scout image are calculated and thesource-to-image distance is determined based on the data defining thespatial configuration of the x-ray source and the collimator and on thedimensions of the scout image. In an embodiment, a method of operating amobile fluoroscopic imaging system includes positioning an x-ray sourceand a DR detector about a patient. Data defining a spatial configurationof the x-ray source and the collimator is stored in the system. Thesystem is configured to determine a source-to-image distance of thex-ray source and the DR detector including by activating the x-raysource and capturing a scout image in the DR detector. Dimensions of thescout image are calculated and the source-to-image distance isdetermined based on the data defining the spatial configuration of thex-ray source and the collimator and on the dimensions of the scoutimage. In another embodiment, a method of operating a mobilefluoroscopic imaging system having a mounted x-ray source, a collimator,and a freely positionable DR detector includes positioning the x-raysource and the DR detector about a patient. Inclinometers are providedon the x-ray source and the detector to determine that the x-ray sourceand the detector are parallel within an acceptable tolerance. Anaperture of the collimator is set to a preselected size and a scoutimage is captured on the DR detector. A size of the radiation field ofthe scout image on the DR detector is determined and increased aperturesize is calculated so that the radiation field of the increased aperturesize fits within borders of the DR detector. The aperture is set to theincreased size and a fluoroscopic examination is commenced.

According to an embodiment of the present disclosure, collimator light502 includes a projector, configured to project information related toradiation beam tracking onto the patient or imaged object during thefluoroscopy session. With this arrangement, the control logic inprocessing system 421 (FIG. 6 ) can control the temporal and spatialpattern of illumination from the collimator light 502, according to thedetected boundaries of the image content generated at detector 404.FIGS. 10A, 10B, and 10C show some different examples and features forthe projected illumination output. For clarity, the patient is notrepresented in FIGS. 10A-C; in practice, the projected outline 30 andother content can appear displayed on and near the patient. Becauseedges of the detector 404 may not be clearly perceptible to the operatoror practitioner, the projected illumination pattern can be useful forindicating positioning status.

FIG. 10A shows projection of a radiation field outline 30 fromcollimator light 502 where there is good positioning of the source anddetector 404. In the FIG. 10A example, outline 30 indicates that theradiation field bounded by the outline is clearly well within the edgesof detector 404 and within the Safe zone S, as described previously.Illumination within and extending to outline 30 can be displayed in anappropriate color to indicate Safe zone positioning, for example.

The example of FIG. 10B shows a change in the projected illuminationfrom collimator light 502 where the scout or fluoroscopy radiation fieldextends past the boundaries for Safe zone S and into Warning zone W.Collimator illumination can change color accordingly to indicateposition status. Further, a portion of outline 30, or the completeoutline, can change color to alert the attending staff. A text message40 can display informative or instructional information that can be usedto aid in dynamic adjustment of the tube head position while thefluoroscopy session continues, for example. An arrow or other symbol canbe projected as a warning or to indicate a recommended correction.

The example of FIG. 10C shows how projection may change when theradiation field extends past the Warning zone W and into the Terminationzone Z, so that emission is suspended. Collimator illumination canchange to a suitable color, such as red, to indicate this condition. Inaddition, where projection apparatus is provided, the color of part orall of outline 30 can be changed to reflect this condition. Similarly,colors and appearance of symbols can also be suitably changed.

The logic flow diagram of FIG. 11 shows a sequence for fluoroscopyimaging while tracking the position of the radiation field from thex-ray source. This sequence can be executed by processing system 421(FIG. 6 ) before and during the fluoroscopy session. An initialacquisition step S1110 acquires a scout image for checking the positionof the radiation field, as recorded by the detector. A field boundarycheck step S1120 senses and reports the position of the receivedradiation field, as recorded by the detector, to determine whether ornot the field ties fully within the Safe zone S. If outside Safe zone S,a problem reporting step S1130 controls the illuminated content fromcollimator light 502, such as controlling color, timing, and otherappearance factors, as is described with reference to the examples ofFIGS. 10A-10C, The operator corrects the positioning error and canacquire a second scout image as shown, repeating steps S1110 and S1120as needed in order to assure position of the radiation field within theSafe zone S.

Once conditions required for initial placement using the scout imagehave been satisfied, fluoroscopy imaging can commence. Continuing withFIG. 11 , a looping sequence follows, continually checking the positionof the radiation field throughout fluoroscopy acquisition. Anacquisition step S1140 acquires a fluoroscopy image frame. A fieldboundary check step S1150 determines whether or not the radiation fieldof the acquired frame is detected within the Termination zone Z; if so,a disable and reporting step S1160 disables radiation emission forfluoroscopy until the field position is set correctly and reports thepositioning problem on the control monitor and/or using the collimatorlight display. For example, step S1160 can disable the operator footpedal 426 (FIG. 6 ). If the radiation field does not impinge theTermination zone Z, fluoroscopy can continue. A second field boundarycheck step S1170 checks for field impingement onto the Warning zone W. Areporting step S1150 displays a warning message or other signal butallows imaging to continue. Processing continues through the loop ofsteps S1140, S1150, S1160, S1170, and S1180 until the fluoroscopysession is terminated.

It is noted that when fluoroscopy is disabled in step S1160, operationmoves to step S1110 for scout image acquisition, enabling thepractitioner to make and verify any needed positional adjustments forreturning to fluoroscopy.

There can be advantages to allowing the operator to set the boundarythresholds for Safe zone 5, Warning zone W, and/or Termination zone Zand to select other operational parameters suitable to the patient andthe procedure for which fluoroscopy is used.

FIG. 12 shows an exemplary operator interface 1210 that allowsconfiguration of dimensions for Safe, Warning, and Termination zones aswell as determining the appearance of the projected information fromcollimator light 502.

A dimension control function 1220 enables adjustment of zones to suit aparticular system. As shown in FIG. 12 , multiple Warning zones W can beset up, with corresponding thresholds and behavior settings. Values canbe set up according to various dimensional metrics, such as inches,millimeters, number of pixels, percentage of active detector area, orother criteria.

A display control function 1230 controls the appearance of the projectedcollimation light for radiation field representation or outline, messagecontent, and other features.

According to an embodiment of the present disclosure, a timeout entry1240 can be provided in order to momentarily delay termination ofradiation emission when the radiation field has been detected within theTermination zone Z. The default timeout can be preset at manufacture orcan be operator-configurable. An optional second timeout can be set bythe operator, to allow an operator override, such as at some time duringthe fluoroscopy session. This second timeout can add a measure of timein addition to the default timeout. Time periods can alternately bemeasured in terms of total dose or number of image frames. Alternately,time periods used can be clock time for x-ray enablement, independent ofactual exposure time. The timeout period can vary based on factors suchas relative area of the radiation field that is detected outside Safezone S, for example.

According to an embodiment of the present disclosure, a weighted timeoutis provided based on percentage area of the radiation field within theSafe zone S or Warning zone W. Thus, for example, the full timeoutperiod applies when less than 2-4% of the radiation field is detectedwithin Warning zone W and the balance of the field lies within Safe zoneS. The timeout period is reduced, such as in proportion, as the amountof the radiation field detected outside Safe zone S decreases, orinversely as the amount within Warning zone W increases.

In this disclosure, an embodiment of the present disclosure may bedescribed as a software program. Those skilled in the art will recognizethat the equivalent of such software may also be constructed inhardware. Because image manipulation algorithms and systems are wellknown, the present description will be directed in particular toalgorithms and systems forming part of, or cooperating more directlywith, the method in accordance with the present disclosure. Otheraspects of such algorithms and systems, and hardware and/or software forproducing and otherwise processing the image signals involved therewith,not specifically shown or described herein may be selected from suchsystems, algorithms, components and elements known in the art.

A computer program product may include one or more non-transitorystorage medium, for example; magnetic storage media such as magneticdisk (such as a floppy disk) or magnetic tape; optical storage mediasuch as optical disk, optical tape, or machine readable bar code;solid-state electronic storage devices such as random access memory(RAM), or read-only memory (ROM); or any other physical device or mediaemployed to store a computer program having instructions for controllingone or more computers to practice the method according to the presentdisclosure.

The methods described above may be described with reference to aflowchart. Describing the methods by reference to a flowchart enablesone skilled in the art to develop such programs, firmware, or hardware,including such instructions to carry out the methods on suitablecomputers, executing the instructions from computer-readable media.Similarly, the methods performed by the service computer programs,firmware, or hardware are also composed of computer-executableinstructions.

The invention claimed is:
 1. A method of radiographic imaging, themethod comprising: providing a digital radiographic (DR) detector;energizing a radiation source aimed at the DR detector; detecting aradiation field on the detector, the radiation field generated by theenergized radiation source; and providing a warning when the radiationfield is determined to be within a predefined warning zone on thedetector.
 2. The method of claim 1, further comprising selectivelydefining dimensions of the warning zone on the detector by using aprogrammable software function having selectable warning zonedimensions.
 3. The method of claim 2, further comprising selectivelydefining dimensions of a termination zone on the detector by using aprogrammable software function having selectable termination zonedimensions.
 4. The method of claim 3, further comprising turning off theradiation source when the radiation field is determined to be within thetermination zone.
 5. The method of claim 2, wherein the step ofselectively defining dimensions of the warning zone comprises selectingnumerical x and y coordinates of the warning zone.
 6. The method ofclaim 1, further comprising turning off the radiation source when theradiation field is determined to be within a predefined termination zoneon the detector.
 7. The method of claim 6, further comprising energizingthe radiation source in response to entry of an operator overrideinstruction.
 8. The method of claim 1, further comprising illuminatingthe radiation field using a first color collimator light, orilluminating the radiation field using a second color collimator lightdifferent from the first color collimator light when the radiation fieldis determined to be within the predefined warning zone, or illuminatingthe radiation field using a third color collimator light different fromthe first color collimator light and the second color collimator lightwhen the radiation field is determined to be within a predefinedtermination zone.
 9. The method of claim 8, further comprisingpredefining a color of the collimator light by using a programmablesoftware function having selectable collimator light colors.
 10. Amethod for radioscopic imaging, the method comprising: energizing aradiation source aimed at a digital radiographic detector; detectingwhether a radiation field from the energized radiation source is withina predefined warning zone on the detector; and providing a visual oraudible warning when the radiation field is detected to be within thepredefined warning zone.
 11. The method of claim 10, further comprisingdefining dimensions of a termination zone on the detector using anoperator interface having selectable termination zone dimensions andpreventing energizing the radiation source when the radiation field isdetected to be within the termination zone.
 12. The method of claim 11,wherein the step of defining dimensions of a termination zone comprisesselecting numerical x and y coordinates of the termination zone.
 13. Themethod of claim 10, further comprising preventing energizing theradiation source when the radiation field is detected to be within atermination zone on the detector.
 14. The method of claim 13, furthercomprising energizing the radiation source in response to entry of anoperator override instruction.
 15. The method of claim 10, furthercomprising illuminating the position of the radiation field with respectto a subject to be radioscopically imaged.
 16. The method of claim 10,further comprising illuminating the radiation field when detecting thatthe radiation field is within the predefined warning zone.
 17. Themethod of claim 16, further comprising predefining a color of a lightsource for illuminating the radiation field when detecting that theradiation field is within the predefined warning zone.